Compact industrial vehicle

ABSTRACT

A compact industrial vehicle, for example in the form of a compact loader, has four steered wheels may be swiveled through 180° between two end positions. The vehicle has a straddling or gantry chassis and the wheels are mounted on straddling axles, whose axle members are placed towards the top of the wheels. Running down from the axle members there are oblique wheel mounting legs ending at the space inside the wheels, in which there is a drive for the final drive step down gearing. Therefore the vehicle is optimally maneuverable while the ground and the tires are not subjected to heavy wear, there are good running characteristics and the driver is able to board the vehicle easily.

The present invention relates to a compact industrial vehicle which isfitted or, is adapted to be fitted, with an appliance. More speciallythe invention relates to a compact loading vehicle with a loading shovelor if desired with a digging contrivance, a snow plow or some otherappliance.

Operations undertaken with such attachments frequently have to takeplace in situations where space is at a premium, as for example onhighway construction sites, in narrow streets, in ships' holds or inconnection with indoor building or assembly operations. For suchconstruction sites highly maneuverable compact motorized loaders may beused that are sold under the name of "Bobcat". With such vehiclessteering is by braking that wheels on one side or even turning them inthe opposite direction to the other side so that a very tight turningcircle is possible. However, there is then the drawback of rapid tirewear and substantial loading or churning up of the ground; furthermorethe vehicle is hard to drive, because the wheel spacing has to be small.Moreover to shorten the vehicle the loading means is pivoted on the backend on both sides of the vehicle and runs forwards along the side of thevehicle, but this makes it harder for the driver to get on and off thevehicle and obstructs his view and the vehicle is more likely to tipover. A further substantial shortcoming is the small ground clearance.

On the other hand the construction of very small, maneuverableindustrial vehicles with steered driven axles also runs up againstconsiderable difficulties since conventional wheel steering systems onlymake it possible for the wheel on the inner side when cornering to beswiveled through about 40°, although steered and driven axles have beendesigned to swivel through up to 60°. It has not however so far beenpossible for wheels on driven axles to be swiveled through larger anglesbecause of the design of the shafts with two universal joints.

Furthermore an industrial vehicle as been proposed in the GermanOffenlegungsschrift specification No. 2,902.446 with four driven wheelsthat are mounted on separate upright wheel legs. The drive shaft is inthis case placed within a hollow steering shaft and the means forsupporting the wheel bearing and a bevel transmission for connection ofthe upright driving shaft with the horizontal driving shaft are placednext to each wheel near its axis. This known vehicle, that was designedas a light-weight and light-duty vehicle, has a quite inadequate groundclearance because of the components associated with the wheels, and thedriver has to keep such lack of clearance constantly in mind morespecially during off-road operations. Furthermore the known design ofvehicle was hardly suitable for use with appliances like shovels havinga heavy power requirement for operation.

In connection with attempts in the prior art to design industrialvehicles which may be steered in all directions (see the GermanGebrauchsmuster Pat. No. 8,031,892), there was a proposal to mount thewheels of a fork lift truck like the wheels of a gantry orload-straddling crane on special freely swiveling legs running radiallyupwards from the wheels. Each wheel hub was then to be fitted with ahydraulic or electric drive motor. For steering, the wheel legs were tobe swiveled by way of bevel gearing. Because all of the vehicle body wasplaced higher up than the level of the tops of the wheels, the vehiclewas relatively tall and its center of gravity was correspondingly highup, so that stability was impaired and might well be insufficient forlifting heavy loads.

In a further proposal (see German Offenlegungsschrift specification No.2,905,528) aimed at improving the design of the vehicle and morespecially to increase stability and make it easier to board, parts ofthe chassis were to be placed like a gantry over the wheels. This knownform of chassis had an outer chassis with the legs and a lower innerchassis obstructing the swiveling of the wheels. This form of chassisdesign would not be suitable for a compact industrial vehicle with ahigh degree of maneuverability.

One purpose of the present invention is that of creating a compactindustrial vehicle of the sort referred to, which has a steering systemenabling it to be maneuvered in a very tight space, while at the sametime being endowed with a high degree of stability and a good groundclearance.

This purpose is effected by the invention wherein the combination of agantry or straddling chassis running over the wheels with the gantryaxles preferably running transversely and generally at the same level asthe tops of the tires of the wheels means that the vehicle design isgenerally relatively squat, while at the same time wheels swivel througha very large angle and there is a large ground clearance between thewheels. The outcome is that the vehicle is of universal application forwork in restricted spaces, that is to say including operations on softground or when there are heavy sideways forces acting on the vehicle.

To give a further improvement in ground clearance, it is possible tohave a transmission with a large step down ratio in the wheel body. Astill further contribution to reducing the chafing or scouring action onthe tires so that there is a beneficial effect with respect to the floorwear rate and possible damage thereto. However, it is possible totolerate a certain positive or negative king pin offset that ispreferably still within the tire contact patches. This value for theking pin offset and the dimensions results in the limitation of theswivel of the wheels being by the axle member and the limitation may besuch that the wheel swivels through 180° or slightly more.

A programmed drive system therefore contributes further to the reductionof chafing of the tires, because when turning in a tight circle thecontact patch of the tires is not changed. The programmed action usedmay be an electronic one or produced by cams in a known way (see theGerman Offenlegungschrift specification No. 2,441,995). If a certaindegree of inaccuracy of the steering may be tolerated, program controlmay be by way of a lever or the like system.

Due to the steering axis inclination and camber when the wheel isswiveled between its two end positions its inner face will define aconical space as needed to allow for the presence of the axle member.This is expedient in connection with enabling the wheels to be swiveledthrough 180°. In this respect the purpose of the measure to makecrabbing (i.e. travel at 90° to the straight ahead direction) possibleinasfar as in the limit position two wheels may be swiveled through180°, on swiveling the wheels more and more so that the turning circleis increasingly diminished till the wheels are placed completelytransversely, the settings of the wheels may be such, for example, thatthe front wheels thrust the vehicle to the left whereas the back wheelsthrust it to the right. If the vehicle is now to crab, it will benecessary either for one of these pairs of wheels to be reversed with areversing gear or one pair to be swiveled through 180°.

In the case of a further programmed mode of steering control it ishowever possible for the vehicle not only to be driven at 90° to thestraight ahead direction but furthermore at any other angle to thestraight ahead direction or obliquely. As an example, the steering armsmay be joined together by selected steering tie rods that make use ofthe different components of transverse motion of the arcuate loci of thepivot points of the tie rods on the arms in order to produce differentsteering movements by the different linkage systems. With parallelalinement of the wheels the driving directions have to be the same inall cases. Steering linkages are known in another context, see forexample the German Offenlegungsschrift specification No. 2,349,177.

As will have been made clear, the idea of the invention for the designof a compact industrial vehicle makes possible the construction of suchvehicles that are not only very maneuverable but furthermore are verystable and have very good driving characteristics. As an example ofthis, the axle arm steering system makes possible a wheel base which isequal to at least 1.5 times the wheel diameter or for example in thecase of an actual construction tested, more than 1.8 times the wheeldiameter. This large wheel base in conjunction with the gantry orstraddling chassis furthermore makes it possible to board the vehiclefrom the side. In this respect, the space under the axle mamber, i.e.the space that is confined at the sides by the wheel supports or legsrunning at a slope into the concave parts of the wheels, is to be keptfree, or, if anything, parts of steering arms may be mounted on thelower side of the axle member in addition. Adjacent to the axles thisspace is used to allow for the swiveling motion of the wheel. Theselection of the height of the axle members on the one hand and the freespace thereunder on the other hand makes possible a good combination ofa low center of gravity and good ground clearance. A still furthercontribution is rendered in this respect by the straddling chassis thatis at a lower level between the wheels.

Another feature of the invention is to produce the right relationshipbetween the size of the wheel on the one hand and of the vehicle on theother, and to make it possible by the programming of the steering and bythe wheel dimensions, even making it possible to have a very large wheeldiameter.

To achieve the compactness and low center of gravity it is preferred toplace the driving engine to the side of the driver's seat (which hasbeen used in another context, see U.S. Pat. No. 3,933,224), which isbest used in combination with the feature of locating the crank shaftaxis at a level lower than the wheel top. This makes it possible for thespace under the axle member of the engine to be kept free. Furthermorethe vehicle does not need to be made any longer.

It is possible to make the vehicle safer and more convenient for thedriver than known compact industrial vehicles which the driver has toboard by scrambling over the appliance, as for example a shovel. Lastlythe vehicle is designed for accurate operation within very confinedspaces under true working conditions. If the appliance on the vehicle isa loading shovel, the driver will be able to see the front edge from hisseat and feel the full benefit of the maneuverability of the vehiclewhen working between obstacles or the like.

Further details, useful effects and developments of the invention willbe seen from the following account of preferred working examples thereofusing the figures.

FIG. 1 is a diagrammatic side view of a compact industrial vehicle, thatis to say a dwarf loader with a space saving design and a high degree ofmaneuverability.

FIG. 2 is a diagrammatic cross section through the driven wheels in thestraight ahead position and at the greatest range of swivel angle.

FIGS. 3A-G are diagrammatic plan views of different settings of thewheels for steering.

FIG. 4 is a perspective view of the straddling or gantry chassis of thevehicle as in FIG. 1.

FIG. 5 is a partly sectioned front view of one axle of the compactindustrial vehicle.

FIG. 6 is a side view of the axle to show the wheel in its two extremeswivel positions.

FIG. 7 is a vertical section through a wheel with a wheel mounting legas part of a different design.

FIG. 8 is a side view of the axle with the wheel mounting leg as in FIG.7 but with the wheel sectioned in its two extreme swivel positions.

FIG. 1 shows a compact industrial vehicle in keeping with the inventionin the form of a compact shovel loader having a straddling or gantrychassis 1, front wheels 2, back wheels 3, a driver's cabin 4 and aboom-mounted appliance in the form of a loading shovel 5. The industrialvehicle is very space saving and highly maneuverable. To give some ideaof the dimensions, by way of example, a medium sized vehicle of a seriesmay have an overall height of 2000 to 2300 mm, an overall length withoutthe appliance of 2300 to 2800 mm, a wheel diameter including tires of800 to 900 mm and a track of 1000 to 1200 mm. The shovel 5 is pivotallymounted by way of the boom at a pivot point 6 located at the back of thedriver's cabin on one side of the vehicle so that the boom is not in theway of the driver when it comes to getting into and out of the cabin 4on the other side. The bottom of the windshield 7 is at a low enoughlevel for the driver to have a good view of the area right in front ofhim and if the appliance is a loading shovel he will be able to see thefront edge thereof from his seat. To this end the seat is relatively farforward and steering is by way of a handlebar 8 that only takes up asmall area. The wheels 2 and 3 are placed as far apart as possible atthe very ends of the chassis so that the vehicle has good drivingcharacteristics and has a high resistance to turning over while at thesame time possessing a substantial ground clearance for running on roughground.

The high degree of maneuverability of the vehicle, outdoing that of adrive steered compact industrial vehicle, is a consequence of the waythe wheels are mounted. The industrial vehicle has four steered wheelsmounted on a straddling axle structure so that they each swivel througha steering range of 180° symmetrically about the straight aheadposition. In other words, the wheels swivel through 90° in eitherdirection from the straight ahead setting, see FIG. 2. In fact theswivel range may be somewhat in excess of 180° and may be 183° forexample.

The drive of the separate wheels may be from a central transmission,from transmissions each for two of the wheels only, or from individualtransmissions drives for the wheels. The drives are in each case by wayof a shaft placed in the straddling structure, a design that is verymuch cheaper and more space saving than one using hydraulic wheel hubmotors for example.

FIG. 3 shows different settings into which the wheels may be swiveledand directions of driving. In FIG. 3a the reader will see the straightahead setting and in FIG. 3b the wheel setting on turning round a middlepoint M, which when the wheels are swiveled even further as in FIG. 3cwill end up by being a vertical line on a side of the vehicle. In thesetting of FIG. 3d all the wheels are swiveled as far as they will go,two of the wheels, that is to say either the front wheels 2 or the backwheels 3, having been swiveled through 180° so that the vehicle crabs.In the wheel setting of FIG. 3e only two of the wheels are being driven,whereas the other two wheels are coasting and the center of the turningcircle M is between the two coasting wheels. FIG. 3f shows thepossiblity of driving obliquely with the vehicle facing straight ahead,if it is possible for the wheels to be steered in this way. A conditionfor this type of maneuvering is that the driving means for each pair ofwheels mounted on an axle is able to be steered independently from theother(s). Such independent control of the driving means and positions ofswivel furthermore makes possible the setting of FIG. 3g in which thevehicle is turning with a sort of roundabout or carousel effect aboutits middle vertical axis and a zero turning circle radius. The settingof FIGS. 3f and 3g are more specially possible when the wheels are ableto be set at any given point or angle within their range of swivel andare then driven in either direction as may be necessary.

FIG. 4 is a perspective view of the chassis 1 that has a straddling organtry configuration. It has sections 11 placed at a higher level overthe wheels and sections 12 at a lower level between the wheels andrising and falling sloping sections 13 joining same together. Betweenthe high level chassis sections 11 there are cross pieces 14. As may beseen from FIGS. 1, 2 and 4 the space under the high level sections 11 isfully available for accommodation and swiveling of the wheels. Thisproves to be necessary because in their extreme swivel positions therewill only be very little clearance between the wheels in the breadthdirection or in other words, when looking in the length direction of thevehicle it will only be possible to see a small space between thewheels.

The low level wheel sections 12 have the general effect of lowering thecenter of gravity and improving the design of the driver seat facility,because the position of the driver is relatively low down and near tothe field of operations and he will be able to get on and off thevehicle safely and conveniently over the chassis part 12.

FIG. 5 is a partly sectioned front view of the front axle for example tomake clear the straddling or gantry axle construction. It is composed ofan axle member 15 and wheel mounting legs 16 running down therefrom atan angle to the vertical. These legs 16 may be turned in the member forswiveling the wheels and they are pivotally joined up with the axlemember or casing by way of support sections 17 that run down from therest of the axle. Each wheel is bearinged on its leg 16 within thedished part of the wheel member 18. The wheel legs 16 each have alengthways axis 19 coinciding with the pivot axis thereof and which inthe present working example is oblique and within the vertical axialplane of the wheel in question. It makes an angle of 79° to thehorizontal so that there is an angle α of inclination of the steeringaxis or "king pin" inclination of 11°. The radial middle plane 20 of thewheel 2 has a camber angle β of 2°. The axis 19 and the middle plane 20both cut through the tire contact patch on the ground 21 area butseparately and in fact for design reasons a steering axis or "king pin"offset 22 is tolerated. The design is however such that this offset isnot overly large. If it were large, it would be at the cost of a loss ofground clearance.

The wheels 2 are swiveled by a steering arm member 26, that has twosteering arms 27 over the body of the axle 15 and a steering arm 28thereunder. The steering arms 27 and 28 are torque-transmittingly joinedtogether. One of the lever arms 27 is connected with a power steeringsystem, more specially in the form of a hydraulic cylinder and the otheris joined by a track rod (not marked) with the corresponding steeringarm of the other wheel of the same axle. The lever arm 28 is joined upby way of a link 29 with the wheel mounting leg 16 with a step-uplevering effect for swiveling the leg 16.

On swiveling the steering member 26 through 90° for example the wheelmounting leg 16 will be swiveled through 180° so that the wheel isturned into a completely transverse position and furthermore it willbear an angle to the ground 21 of the order of 77°, answering to anangle to the vertical of 13° which results from the steering axisinclination and the camber as measured in the straight ahead wheelsetting. This oblique setting of the wheels does not entail anyundesired effects for vehicle statics and for driving characteristicswhen maneuvering; it is however necessary to leave room for the axlemember (see FIG. 6) beside the top of the wheel in the extreme positionsof the wheel.

FIG. 6 makes it very clear how little space is left for the body of theaxle and more specially the forked end thereof when a wheel is swiveledout to its full extent. The swivel through 90° in both directions ispossible because the wheel mounting leg fits into the concave side ofthe wheel.

The drive is transmitted by way of a differential 32, a half shaft 33, afirst bevel wheel drive 34, an inbetween shaft 35, whose axis is linedup with the lengthways axis of the wheel leg 16, and a second bevelwheel drive 36 to a pinion shaft 38 parallel to the axis 37 of the wheel2. The drive is then further transmitted by way of spur gearing 39 witha step down effect to the wheel hub. It will be seen from this that,within the body of the axle and the wheel support legs, the drive istransmitted at a relatively high speed with a low torque in comparisonwith the wheel hub speed.

When the wheels are swiveled into their extreme positions they comequite close together near the lengthways median plane of the vehicle sothat the design has to be such that the space under the straddling axleis free on the one hand to get a large ground clearance and on the otherhand for swiveling of the wheels. In this respect the vehicle chassis 1constitutes the lower limit of the vehicle body and the axle members 15are mounted on the lower sides of the cross pieces 14.

The construction to be seen in FIGS. 7 and 8 also makes possible a highdegree of maneuverability and a large ground clearance. The wheel ismounted on a wheel leg 16, that may be named a gantry leg and whosethree main parts are coaxial, namely, an inbetween drive shaft 41, ahollow steering shaft 42 coaxial to the inner inbetween shaft 41 andturning separately from it, and a load bearing structure 43 fixedlymounted on the chassis. The load bearing structure 43 is in the presentcase designed in the form of a sort of housing round the two shafts 41and 42 and runs upwards in the level axle member 15 stretching athwartthe vehicle and in which the half shaft 33 coming from the differential32 is housed, said shaft driving the inbetween shaft 41 by way of thebevel drive 34.

There are a number of different ways of designing the drive. It may forexample be run from a central transmission by way of a universal jointor stiff shaft to the upper bevel gear pair of a wheel drive. It ishowever furthermore possible for the two upper bevel gears of the frontor back wheels to be joined up together by way of shafts placed in theaxle members so that the driving system would resemble that of aconventional vehicle with axles. Furthermore it would be possible forthe drive system to be a hydrostatic one, in which respect there wouldbe one motor and one pump for the two front wheels and a motor and pumpfor the back wheels. It would then for example be readily possible toreverse the wheels of one axle when all wheels are swiveled into theirextreme positions so that crabbing of the vehicle would be possible.

The coinciding axis of turning of the inbetween shaft 41 and of thesteering axis 42, that is to say the lengthways axis of the wheel leg16, is in the case of this form of the invention out of plumb by 13° asa steering axis inclination angle and is in a plane that is normal tothe plane of the wheel and the ground and it contains the axis ofrotation of the wheel. The lengthways axes of the wheel legs 16 of thetwo front wheels 2 are in a first plane and the lengthways axes of thewheel legs 16 of the two back wheels 3 are in a second plane parallelthereto.

The wheel 2 or 3 itself has a camber angle of 2° so that between thelengthways axis of the wheel leg 16 and the wheel plane there is anangle of 15°. Making good use of this angle in the construction thefinal step down gearing, transmitting the drive to the wheel, is placedwithin the concave part of the wheel. This final step down gearing ismade up of a bevel pinion 44 mounted on the inbetween shaft 41 and abevel gear 45 meshing therewith which is keyed on the wheel stub axle.Although by having the drive gearing in the lower part of a wheel axlehousing 46 there is no trouble with lubrication, the transmission ofpower and the space requirements are less favorable than in the spurwheel transmission system as used in FIG. 5.

The final step down gearing is on the one hand to be such that the stepdown effect takes place as far as possible near the wheel, so that thepower transmitting components may be kept small and light in weight. Onthe other hand however the final drive should not, as far as possible,stick out from the wheel outline in order not to rob the vehicle of itsground clearance. The design data including the angle of the leg are forthis reason to a large degree dependent on the space within the concavewheel member and, for this reason, on the wheel size and tire breadth.

The wheel axle housing 46 is welded to the hollow steering shaft 42 moreor less as an extension thereof and the wheel is bearinged in thehousing 46. The housing 46 is swiveled together with the wheel aroundthe lengthways axis of the wheel leg 16 when the steering shaft 42 isturned, something that takes place in the present example by way of achain drive using a chain sprocket wheel 47 and a chain 48.

FIG. 8 shows, looking in the direction normal to the plane ofinclination of the wheel leg 16, the two extreme swivel positions of thewheel 2 or 3, the wheel being sectioned through the concave part thereof(avoiding the center of the wheel) to make the figure clearer the wheelonly occupying one of the two positions at a time. The angle between thewheel leg 16 and the wheel plane has such an effect in these two extremepositions that the wheel has an inclination to the vertical that isequal to 15°. This inclination is not great enough to have any undesiredeffects.

As may be seen from FIG. 8, the axle member 15 and the chain 48 areclear of the wheel in its two extreme positions of the wheel so that itis not necessary for the axle member to be placed at a higher level thanthe top of the wheel. If a position near the top of the wheel stillgives the desired ground clearance, then this position of the axlemember 15 is highly expedient as regards enabling the axle to be verystrong in design.

The FIGS. 7 and 8 show the lengthways axis 19 of the wheel leg 16 andthe wheel diameter in the radial median plane 20 of the wheel runningthrough the tire contact patch and meeting at a point therein so thatthe steering axis offset is zero. When the wheel is swiveled it is infact turned on its ground contact patch without any displacement, andthis makes the vehicle easy to steer with only a small amount of effectbeing needed.

Without any change in FIG. 7 or of an end part in FIG. 5 the describeddesign might furthermore be so modified that the plane of inclination ofthe wheel leg 16 (ie.e. the vertical plane containing the axis of theleg) would not be in the transverse direction of the vehicle but in thelength direction thereof. The settings to be seen in FIGS. 6 and 8 wouldthen be the settings for straight ahead travel, whereas the settings ofFIGS. 5 and 7, that is to say the middle position of the steeringswivel, would be the position for crabbing. This configuration would belikely to be preferred if for example the housing designated as the axlemember 15 were to run along the side of the vehicle in the lengthdirection for design reasons. However the design would then be such thatfor normal driving the wheels would be turned into the oblique positionto be seen in FIGS. 6 or 8, which would be perfectly in order formaneuvering but would hardly be very suitable for driving straight.

As may be more specially seen from FIG. 7 the ground clearance is notreduced by the design of the final step down gearing. The wheel legrunning upwards at a slope, whose lower end is the wheel axle housing46, is not likely to jam on obstructions on the ground and there is thefull benefit of the gantry.

The steering action, which in FIG. 5 involves operation of the steeringmembers 26, is brought about by linear motors; constructions using onelinear motor per wheel, one linear motor per axle or one linear motorfor the complete vehicle with transmission of the steering action by wayof the steering linkage and a drag link are possible. By making theright choice of the means for controlling the hydraulic linear motors asophisticated operation of the vehicle is made possible. It is assumedthat the piston stops on the two sides in the linear motor correspond tothe two 180° apart extreme positions of the wheels. The cylinders of thelinear motors are so designed that they are hydraulically balanced. Inthis respect the displacement volume of the cylinder of the first linearmotor is expelled into the cylinder of the second linear motor and so onso that there is synchronous operation of the linear motor. At the endpositions of the pistons the cylinders of the linear motors havesynchronizing settings, that is to say an overflow by which anyirregularities, as produced by possible differential leakage from theseparate cylinder seals, are compensated for. Furthermore the linearmotors are so conceived that those of the front wheels 2 or those of theback wheels 3 may be switched over from the one extreme position intothe other extreme position.

This switching over from one end or extreme position to the other isneeded as a precondition to drive the vehicle sideways as the next stageafter driving in a circle if there is no facility for reversing two ofthe wheels. In the case of the program for oblique travel with thewheels parallel there is in any case a common direction of the wheels asan end setting.

A reversible drive for the two front wheels 2 on the one hand and forthe two back wheels 3 separately and independently or only for the frontwheels 2 or in fact the back wheels 3, is not overly complex instructure and cuts down tire wear and damage to the ground so that it isto be preferred from more than one point of view.

Programmed steering action, in which the wheel planes are alwaystangential to the cornering radius to reduce tire chafing, is possible(although not shown in a figure), by having the steering wheel joinedwith a transmission that drives two hydraulic cylinders with pistons,that is to say linear pumps by way, for example, of step down gearingand one or more cams or with the help of a variable velocity ratiodrive, as for example one with elliptical gear wheels, or one havingsuitably dimensioned lever linkages. The linear pumps would then in theone case drive the wheels on the left hand side and the other woulddrive the linear motor or motors of the wheels of the right hand side.The linear motors of the wheels of the left side and those of the wheelsof the right side would in each case be balanced, that is to say joinedup in series, synchronization being possible in the end or in the middleposition. The cam outline would be such that the volumes supplied to thelinear motors of the two sides would be different in such a way thatthere would be the desired agreement or alinement of the amounts ofwheel swivel on the two sides.

In keeping with a preferred form of the industrial vehicle, the axlemember to the front on the one hand and to the back on the other jointhe wheel legs and one of the axle members, on which the two wheel legsare rigidly fixed, is in the form of a jointed cross shaft axle so thatthere is better engagement with the ground. As explained, the axlemember with the wheel leg, that contains the gantry or straddling drivein the form of a bevel drive, is placed at a lower level than the top ofthe wheel, something that is made possible by the sloping wheel leg andthe limitation of the wheel swivel to 180° with the free space resultingtherefrom (FIGS. 6 and 8).

In order to save space, the drive engine 51 is placed to the side, i.e.to the left or the right of the driver, so that the lengthways axis ofthe engine, that is to say the axis of the crank shaft, is placed atroughly 90° to the lengthways axis of the vehicle and the engine isplaced in the middle third of the wheel base, that is to say of thespace between the front wheels and the back ones so that the crank shaftaxis may be placed at a lower level than the tops of the wheels withoutthis limiting swiveling of the wheels. The sheet metal floor of thevehicle on which the driver puts his feet is at a higher level than anextension of the crank shaft axis so that the engine and the center ofgravity of the vehicle are relatively low and there is an economic useof the space available, while at the same time the ground clearance,equalling for example 400 mm, is still quite large.

I claim:
 1. A compact industrial vehicle comprising a frame (1)extending in the normal forward travel direction, wheel support legs(16) each having a lengthways axis mounted on said frame, four steerableand powerable wheels (2, 3) suspended from said frame (1) by said wheelsupport legs (16), each said wheel having a wheel rim with said wheelsupport extending upwardly from said wheel rim to said frame, relativeto the forward travel direction of said wheels (2, 3) said wheels aredisplaceable from the forward travel direction into a lateral direction,wherein the improvement comprises:(a) frame (1) is formed as amulti-level construction including frame segments (11) located abovesaid wheels and second frame segments located vertically below saidfirst frame segments and arranged between the wheels in the normalforward direction and third frame segments (13) extending upwardly andobliquely of the vertical between said first and second frame segments;(b) said wheel support legs include horizontal axles (15) located at theupper part of said wheels with said wheel supports extending downwardlyfrom said axles (15) to said wheels (2, 3); (c) in the verticaldirection said axles (15) are positioned between the lower side of saidfirst frame segments (11) and the center of said wheels (2, 3); (d) amotor (51) for driving said wheels is located on the upper side of saidsecond frame segments; and (e) said frame having a front end and a rearend spaced apart in the normal travel direction and a pair of sidesextending in the normal travel direction between the front and rearends, an operator station located on said frame in the region of andabove said second frame segments with an entrance to said operator'sstation on one said side of said frame, and a boom for mounting aworking attachment articulated to said frame behind said operatorstation in the normal travel direction and pivoted to said frame on theopposite side thereof from the entrance to the operator station. 2.Compact vehicle, as set forth in claim 1, wherein said wheels arepivotal from the normal travel direction by 90° on each side of thenormal travel direction position so that said wheels can be pivotedthrough approximately 180°.
 3. The compact vehicle as claimed in claim 2characterized in that in the positions in which the wheels (2 and 3) areturned sideways through 90°, parts of the wheels are, in respect of theopposite position on the axle body (15), overlapped.
 4. Compact vehicle,as set forth in claim 1, wherein the distance between the center of saidwheels in the forward travel direction is at least 1.5 times the wheeldiameter and said vehicle having an overall length without attachment ofapproximately three times the wheel diameter.
 5. The compact vehicle asclaimed in claim 1 characterized in that the extension of the lengthwaysaxis (19) of the wheel leg (16) runs through the contact patch on theground of the wheel (2, 3) joined to the leg.
 6. The compact vehicle asclaimed in claim 1 characterized in that the angle of inclination of thelengthways axis of the wheel leg (16) to the vertical is between 10° and16° and the wheels (2 and 3) have a camber angle of the order to 2°. 7.The compact vehicle as claimed in claim 1 characterized in that thewheel mounting legs (16) have steering shafts (42) running to the wheelbearings thereof and each of the steering shafts has a coaxial sprocketwheel (47) acted upon by a chain (48) for steering.
 8. The compactvehicle as claimed in claim 7 characterized by a steering arm (26)acting on each steering shaft (42).
 9. The compact vehicle as claimed inclaim 8 characterized in that the steering arm (26) has a drive (28 and29) connecting it with the steering shaft for acting thereon.
 10. Thecompact vehicle as claimed in claim 8 characterized in that the steeringlever (26) is placed partly over and partly under the axle member (15).11. The compact vehicle as claimed in claim 10 characterized in thatwith the exception of any steering lever parts (28) the space under theaxle member (15) is free.
 12. The compact vehicle in claim 1characterized in that a driver cabin (4) placed round the driver'sstation and has a windshield (7) with a low bottom edge such that thereis a view from eye level of the driver through the windshield to anapplicance (5) coupled with said boom on the vehicle and placed in frontof the front wheels of the vehicle.
 13. The compact vehicle as claimedin claim 12 characterized in that for operation of the steering systemthere is a handlebar (8) placed in the driver's cabin (4).